I've written a custom point cloud shader that requires some uniforms (vectors representing the screen frustum) to be passed to it before a frame can be rendered properly. Typically, I would do this in MonoBehavior.OnPreRender(). All of the Prefabs that depend on this shader have non-existent preview images. Is there any way I could override the preview rendering with my own custom solution, or at least access the preview camera's equivalent to OnPreRender()? I speak of the preview window that usually appears immediately below the Inspector area when examining Prefabs or other Mesh-based objects. Thanks!